WUE Rule Background Information

About the Water Use Efficiency (WUE) Rule

We consider using water efficiently an important part of the planning program. Since 1994 we have used the Conservation Planning Requirements publication to describe how water systems should incorporate water use efficiency into their planning process. While many water systems have based their successful conservation programs on the 1994 document, the Municipal Water Law (MWL) and WUE Requirement replace it.

In 2003, the Washington State Legislature passed Engrossed Second Substitute House Bill 1338, better known as the MWL, to address the increasing demand on our state’s water resources. The law established that all municipal water suppliers (MWS) must use water more efficiently in exchange for water rights certainty and flexibility to help meet future demands. Water systems that are not subject to MWL requirements are subject to the Conservation Planning Requirements of 1994. If you are not a MWS see Appendix U (PDF) of the WUE Guidebook 331-375 (PDF) for requirements.

After the MWL was passed in 2003 the Legislature directed the Department of Health to adopt an enforceable WUE program, which became effective on January 22, 2007. Creating a regulatory WUE program is intended to achieve a consistently high level of stewardship among all municipal water suppliers.
 

Water Efficiency is a Proactive Approach to Protecting Public Health

Drought, climate change, growth demands, and fewer granted water rights all signal a diminishing water supply and the possibility of future water shortages or disruptions. Public health is always at risk during these events. Water systems position themselves to provide a reliable drinking water supply for their customers when they implement an effective WUE program. WUE measures help water systems proactively prevent potential health risks to their customers, which can result in fewer water emergencies. The WUE program requires water systems to pay attention to their usage patterns and water loss, and report annually.

WUE requirements support our common goal of ensuring safe and reliable drinking water in the following ways:

  • Contribute to long-term water supply reliability and public health protection.
  • Promote good and responsible use of the state’s water resources.
  • Ensure efficient operation and management of water systems.

For most water systems, conserving water can be the least costly source of new water supply. Water system managers balance operation and growth costs with customer revenue when making decisions on the future of their water system.

Requirements

You can find the WUE requirements in Chapter 246-290 WAC and in the May 2025 Revised Fourth Edition of the Water Use Efficiency Guidebook 331-375 (PDF). The fundamental elements are:

  1. Planning Requirements—collect data, forecast demand, evaluate WUE measures, and install meters on all customer lines.
  2. Distribution Leakage Standard (DSL) of 10 percent or less water loss.
  3. Goal Setting and WUE Reporting—publicly establish goals with customers and the community, report annually, and renew WUE program at least every 6 years or as part of your regular water system plan update. 

What the WUE Rule Achieves

WUE measures help water systems proactively prevent potential health risks to their customers, which can result in fewer water emergencies.

Using water efficiently helps water systems protect against:

  • Temporary water service interruptions during peak usage.
  • Long-term or repeated water disruptions due to limited water supply.
  • Contamination of the water supply due to leaky pipes.
     

Who This Affects

The Municipal Water Law says that WUE requirements apply to all water systems defined as municipal water suppliers (MWS). An MWS is “an entity that supplies water for municipal water supply purposes.”

Your water system is most likely an MWS if you can answer “yes” to any of the following. My system:

  • Has 15 or more residential service connections.
  • Is owned by a city, town, public utility district, sewer district, or water district.
  • Provides water in a residential manner to a non-residential population that averages at least 25 people for at least 60 days a year.
  • Provides water indirectly for purposes listed in 1 or 2, through the delivery of water to another water system.

If you answered “no” to all these questions, you most likely don’t meet the definition of an MWS and don’t have to meet the WUE requirements. Please contact your regional planner to confirm.

For More Information

Use the links below to find information.

If you have any questions, please email us at wue@doh.wa.gov.